Process of reducing viscosity of nitrocellulose solutions and product thereof



' Patented July 19, 1927.

UNITED STATES. PATENT- OFFICE.

EARLE C. PITMAN, OF PABLIN, NEW JERSEY,- ASSIGNOR '10 E. I. DU PON '1 DE NIEIIIO'URS & COMPANY, OF WILMINGTON, DELAWARE, CORPORATION OF DELAWARE.

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No Drawing.

o o 1 l y This invention relates to a process of reducing the viscosity of nitrocellulosesolutions without substantiall changing the ratio of nitrocellulose to solvent, and to the 5 product of such process, and it comprises subjecting such solutions to the action of a salt of the character hereinafter described.

While it has been known that viscosity could be made lower by hightemperature nitration or by continued bolling of the pyroxylin, both of these methods and relatively inefl'ective as compared with my new process.

I have discovered thatcertain salts, and

particularly the acetates of the alkali-forming' metals such as sodium acetate and calcium acetate, have a remarkable effect on the viscosity of nitrocellulose (pyroxylin) solutions which have not previousl been treated with said salts. Only a smal amount, for example 0.1%, of the salt, based upon the weight of the solution, is required to bring about a substantialreduction in viscosity.

The reduction of viscosity. according to my 0.2fiparts of sodium acetate are incorporated in the above described'solution, and the mixture is allowed .to stand at room temperature (22 C.) for from 1 to 7 days depending upon the viscosity desired.

The proportion of salt used may be varied within wide limits; it willordinarily be be: tween 0.01% and 4% based upon the weight of the pyroxylin solution. i

The pyroxylin solution may be prepared with any ofthe customary solvents such as are expensive one AND raonnc'r Application fled August 11, 1921. Serial No. 481,596.

ethyl or amyl acetate,,acetone, etc. with or without diluents such as benzene, toluene, ethyl alcohol, etc.

Salts which I have found to be particularly eflicient in reducing viscosit are the acetates of the alkali metals and o the alkaline earth metals. The corresponding salts of other lower monobasic aliphatic acrds are also active ample, the formates. Salts of simple diand tri-basic aliphatic acids such as sodium oxalate and sodium citrate exhibit a viscosityreducing action; but to a less degree than the above. mentioned salts of monobasic acids.

' In addition to the and alkaline earth metals, the acetates of been found to be reducers.

The extent of the reduction or viscosity of a nitrocellulose solution after being subjected to the action of a viscosity-reducing agent for various periods is indicated in the following table, giving results of the action at very effective viscosityi 25 invention is effected by incorporating the room temperature f 02% di t t on salt in the nitrocellulose solution to .form a pyroxylin olutions containing 12' to 18% homogeneous mixture, and then either allowpyroxylin th is o ity b in x r d i ing the mixture to stand for several days at ti i t 25 Q r room temperature, that is, between about 22 and 25 C., or mildly heating the mixp -1 (1mm), m

' ture while preventing the escape of solvent.

The new processmay be illustrated by the Initially 15,000cp. 15.00a 6,300 cp. 5,000cp. following example v 1 lomocp .flfiii lTith'ii" "$33: A pyroxylin solution is prepared having n 1 M 00w.

5 the following composition: lfisbbii "T2655 Parts by 1,0000D- weight. Pyroxylin 20 40 1 Oamphor. 3 900p 40 Fusel oil a 10 a I Wood alcohol 67 The invention is not limited to the acetates of alkali metals ammonium, cadmium, cobalt, and zinc have I treatment of pyroxylin solutions with a of salts which will advantageously afiect the finished nitrocellulose plastic or film.

Instead of. allowing the mixture to stand for several da s at room temperature, it may be heate at a temperature of, say,

from 60 to 80 (1., the reduction in viscosity being thereby greatly accelerated. In many cases, however, it is more convenient to simply allow the solution to stand at room temperature until the desired viscosity value has been reached. Ordinarily I prefer to keep the solution at a temperature above 20 C.

The new solutions obtained by the abovedescribed process are characterized by con taining from about 0.01 to 4% of a salt of a lower aliphatic acid, and particularly from 0.2% to 1% of an alkali-forming metal acetate, and by having a substantially lower viscosity than a solution having the'same nitrocellulose-solvent ratio, but free from a viscosity-reducing substance.

I claim 1. The process of reducing the viscosity of a nitrocellulose solution which comprises dissolving therein a soluble salt of a lower, monobasic, aliphatic acid, and allowing the resulting solution to stand until a substantial reduction in viscosity has occurred.

2. The process of reducing the viscosity of a nitrocellulose solution which comprises dissolving therein an alkali-forming metal salt of a lower aliphatic acid, andallowing the resulting solution to stand until a substantial reduction in viscosity has occurred.

3. The process of reducing the viscosity of a nitrocellulose solution which comprises dissolving therein sodium acetate, and allowing the resulting solution to stand until a substantial reduction in viscosity has occurred.

4. The process of reducing the viscosity of a nitrocellulose solution which comprises treating it with from 0.01% to 4% of an alkali-metal salt of a lower, monobasic, aliphatic acid, and allowing the resulting solution to standat least until a substantial reduction in viscosity has occurred.

5. The process of reducing the viscosity of a nitrocellulose solution which comprises treating it with from 0.2% to 1% of sodium acetate, and allowing the resulting solution to stand at least until a substantial reduction in viscosity has occurred.

6. The process of reducing the viscosity of a nitrocellulose solution which comprises a substantial reduction in viscosity has oc-.

curred.

8. The process of reducing the in said solution to the action of an alkali-form ing metal salt of a lower aliphatic acid, and

a substantial reduction in viscosity has occurred.

9. The process of reducing the viscosity of a substantially neutral nitrocellulose solution which comprises subjecting the nitrocellulose in said solution to the action of an alkaliforming metal acetate, and allowing said action to continue at least until a substantial reduction in viscosity has occurred.

10. The process of reducing the viscosity of a substantially neutral nitrocellulose solution which comprises dissolving therein a soluble salt of a lower, monobas1c,- aliphatic acid, and allowing the resulting solution to stand until a substantial reduction in viscosity has occurred.

11. The process of reducingthe viscosity of a substantially neutral nitrocellulose solu tion which comprises dissolving therein an alkali-forming metal salt of a lower aliphatic viscosity of a substantially neutral nitrocellulose solution which comprises subjecting the nitrocellulose allowing said action to continue at least until acid, and allowing the resulting solution to stand until a substantial reduction in viscosity has occurred. I

12. The process of reducing the viscosity of a substantially neutral nitrocellulose solution which comprises subjecting it to the action of from 0.01% to 4% of an alkali-metal salt of a lower, monobasic, aliphatic acid until a substantial reduction in viscosity has occurred.

In testimony whereof I aflix my s' ature.

EARLE C. PIT 

